Method of forming dual damascene metal interconnection employing sacrificial metal oxide layer

ABSTRACT

There is provided a method of forming a dual damascene metal interconnection by employing a sacrificial metal oxide layer. The method includes preparing a semiconductor substrate. An interlayer insulating layer is formed on the semiconductor substrate, and a preliminary via hole is formed by patterning the interlayer insulating layer. A sacrificial via protecting layer is formed on the semiconductor substrate having the preliminary via hole to fill the preliminary via hole, and cover an upper surface of the interlayer insulating layer. A sacrificial metal oxide layer is formed on the sacrificial via protecting layer, the sacrificial metal oxide layer is patterned to form a sacrificial metal oxide pattern having an opening crossing over the preliminary via hole, and exposing the sacrificial via protecting layer. The sacrificial via protecting layer and the interlayer insulating layer are etched using the sacrificial metal oxide pattern as an etch mask to form a trench located inside the interlayer insulating layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.2003-87351, filed on Dec. 3, 2003, the contents of which are herebyincorporated herein by reference in their entirety.

BACKGROUND

1. Technical Field

The present invention relates to a method of forming semiconductordevices, and more particularly, to a method of forming a dual damascenemetal interconnection employing a sacrificial metal oxide layer.

2. Discussion of the Related Art

With the increase of integration degrees of semiconductor devices, theprocess of metal interconnection fabrication is becoming increasinglyimportant in affecting reliability of semiconductor devices. Metalinterconnections are associated with problems such as RC delay, EM(electro-migration), or the like. As one of the methods of solving theproblems, a copper interconnection and a low-k dielectric layer areemployed on a semiconductor device, and a damascene process is used toform a copper interconnection.

A dual damascene process comprises forming a via hole exposing a lowerinterconnection, and a trench intersecting the upper portion of the viahole, filling the via hole and the trench with a metal material such ascopper, and forming a metal interconnection and a via plug at the sametime, through a chemical mechanical polishing (CMP) process. The dualdamascene metal interconnection means a metal interconnection formed bythe dual damascene process.

Further, a dual damascene process of first forming a via hole, and thenforming a trench may be referred to as a via first dual damascene (VFDD)process. However, the VFDD process may provide a lack of process marginsof a photolithography process, in comparison with a typicalphotolithography process of forming a via hole or a trench only.Particularly, as a problem, there may be considered a process margin ofa photolithography process of forming the trench after forming the viahole. Further, etch damage may be caused_in the lower interconnectionexposed through the via hole during the formation of the trench.

A method of preventing etch damage of the lower interconnection andincreasing a process margin of a photolithography process is describedin U.S. Pat. No. 6,329,118, entitled, “Method for patterning dualdamascene interconnects using a sacrificial light absorbing material,”to Hussein et. al.

In the method disclosed in U.S. Pat. No. 6,329,118, a via hole, formedinside an insulating layer, is filled with a sacrificial light absorbingmaterial, and a photoresist pattern is formed on the sacrificial lightabsorbing material to form a trench. Then, using the photoresist patternas an etch mask, the sacrificial light absorbing material and theinsulating layer are etched to form the trench.

The sacrificial light absorbing material reduces substrate reflectivityduring an exposure step in a photolithography process, and improves acapability of controlling a critical dimension (CD) and a CD uniformity.Further, the sacrificial light absorbing material may be dry etched atsubstantially the same rate that the insulating layer may be dry etched,and wet etched at a significantly faster rate than the insulating layermay be wet etched. Therefore, lower interconnects exposed through thevia hole can be protected during the formation of the trench.

However, as the integration of semiconductor devices further increases,a pitch of the trench is further reduced. In the case that a design ruleis 90 nm or less, it is difficult to form a photoresist pattern havingan appropriate pitch just with an exposure step using a KrF laser.Furthermore, in order to etch an insulating layer using the photoresistpattern as an etch mask, a photoresist layer is required to have athickness above a predetermined level. Thus, a photolithography processusing a KrF laser as above is led to a lack of process margins such as aresolution and a depth of focus (DOF). To comply with this, there isemployed a photolithography process using an ArF laser. Thephotolithography process using an ArF laser is advantageous in improvingresolution, and allowing the formation of a much finer photoresistpattern in comparison with the conventional photolithography processusing a KrF laser. However, the photoresist layer for ArF has a loweretch resistance than the photoresist layer for KrF. As a result, an etchprocess of forming a trench using the photoresist pattern as an etchmask cannot provide desired process margins.

Therefore, the dual damascene process of forming a trench using thephotoresist pattern as an etch mask by the method disclosed in U.S. Pat.No. 6,329,118 cannot ensure process margins of photolithography and etchprocesses at the same time, in the recent trends of highly-integratedsemiconductor devices.

SUMMARY OF THE INVENTION

Therefore, the present invention provides a method of forming a dualdamascene metal interconnection, the method being improving processmargins of a photolithography process and an etch process together forthe formation of a trench, without requiring an additional process foraligning a via hole and a trench.

Exemplary embodiments of the present invention provide a method offorming a dual damascene metal interconnection employing a sacrificialmetal oxide layer.

The invention is directed to a method of forming a dual damascene metalinterconnection. The method includes preparing a semiconductorsubstrate. An interlayer insulating layer is formed on the semiconductorsubstrate, and the interlayer insulating layer is patterned to form apreliminary via hole. A sacrificial via protecting layer is formed onthe semiconductor substrate having the preliminary via hole to fill thepreliminary via hole, and to cover an upper surface of the interlayerinsulating layer. A sacrificial metal oxide layer is formed on thesacrificial via protecting layer, and the sacrificial metal oxide layeris patterned to form a sacrificial metal oxide pattern having an openingcrossing over the preliminary via hole, and exposing the sacrificial viaprotecting layer. The sacrificial via protecting layer and theinterlayer insulating layer are etched using the sacrificial metal oxidepattern as an etch mask to form a trench located inside the interlayerinsulating layer.

In accordance with the invention, a photolithography process margin maybe ensured since an ArF laser may be used in a photolithography processof forming the sacrificial metal oxide pattern, and a process margin ofan etch process may be ensured since a trench may be formed using thesacrificial metal oxide pattern as an etch mask.

In accordance with an exemplary embodiment, the sacrificial metal oxidepattern and the sacrificial via protecting layer are removed to exposean upper surface of the interlayer insulating layer and a bottom surfaceof the preliminary via hole. Then, the exposed bottom surface of thepreliminary via hole is etched to form a final via hole exposing thesemiconductor substrate. A diffusion barrier layer and a seed layer aresequentially formed on the semiconductor substrate having the final viahole, and a copper layer is formed on the semiconductor substrate havingthe seed layer to fill the empty space of the final via hole and thetrench. Then, until an upper surface of the interlayer insulating layeris exposed, the copper layer, the seed layer, and the diffusion barrierlayer are sequentially planarized to form a dual damascene metalinterconnection.

In one embodiment, a capping layer may be further formed on thesacrificial metal oxide layer. The capping layer functions to reduce areflectivity of the sacrificial metal oxide layer, and improve acapability of controlling a CD and a CD uniformity. The capping layer ispreferably formed to have a thickness of 100 Å to 500 Å. Further, whilepatterning the sacrificial metal oxide layer, the capping layer may bepatterned together to form a capping layer pattern. The capping layerpattern is preferably removed during the formation of the trench.

Preferably, before forming the interlayer insulating layer, an etchbarrier layer may be formed. The etch barrier layer may include asilicon nitride (SiN) layer, a silicon carbide (SiC) layer, or a siliconcarbon nitride (SiCN) layer. The etch barrier layer functions to preventetch damages on the semiconductor substrate during the formation of thepreliminary via hole.

Further, the interlayer insulating layer is preferably formed of a low-kdielectric layer having an etch selectivity to the etch barrier layer.The interlayer insulating layer may be formed of a silicon oxycarbidelayer (SiOC) or a silicon oxide layer (SiO₂), such as a FSG (fluorinedoped silicate glass) layer, a PSG (phosphorous silicate glass) layer, aUSG (undoped silicate glass) layer, a BPSG (boro phosphorous silicateglass) layer, and a PE-TEOS (plasma enhanced-tetra ethyl ortho silicate)layer, or may be formed by stacking the above layers. Further, theinterlayer insulating layer may be formed of an organo polymer having alow dielectric constant.

Further, the sacrificial via protecting layer may be preferably formedof a spin on deposition (SOD) layer which is dry etched at a dry etchrate which is substantially identical to that of the interlayerinsulating layer, and has a significantly high wet etch selectivity tothe interlayer insulating layer. The SOD layer can fill the preliminaryvia hole even with a small deposition thickness, and has a goodplanarization characteristics thereby increasing a process margin of aphotolithography process. Preferably, the SOD layer may be formed of ahydrogen-siloxane layer, an organo-siloxane layer, or an SOP (spin onpolymer) layer, and more preferably, may be formed of HSQ (hydrogensilsequioxane) or MSQ (methyl silsequioxane).

In one embodiment, the sacrificial metal oxide layer is transparent in avisible wavelength region. The sacrificial metal oxide layer may beformed of an aluminum oxide (Al₂O₃) layer, an indium tin oxide (InSnO)layer, a tantalum oxide (Ta₂O₅) layer, a lanthanum oxide (La₂O₃) layeror a hafnium oxide (HfO₂) layer, or may be formed by stacking at leasttwo layers of the above. More preferably, the sacrificial metal oxidelayer is formed of an Al₂O₃ layer.

Further, the sacrificial metal oxide layer may be formed with athickness of 200 Å to 1,000 Å. As the thickness of the sacrificial metaloxide layer decreases, a process margin of a photolithography processfor patterning the sacrificial metal oxide layer may increase.

In one embodiment, the method further comprises forming a photoresistlayer on the sacrificial metal oxide layer and exposing and developingthe photoresist layer using an ArF laser to form a photoresist patternhaving an opening crossing over the preliminary via hole. Thesacrificial metal oxide layer can be patterned by etching thesacrificial metal oxide layer using the photoresist pattern as an etchmask.

In one embodiment, the method further comprises forming an organicbottom anti-reflective coating (BARC) on the sacrificial metal oxidelayer after forming the sacrificial metal oxide layer. The organic BARCcan be removed prior to formation of the trench. The organic BARC can beremoved using an ashing process.

In one embodiment, the method further comprises forming a capping layeron the sacrificial metal oxide layer prior to formation of the organicBARC. The capping layer can be formed of one material layer selectedfrom the group consisting of poly-Si, FSG, PSG, USG, PE-TEOS, SiOC, SiN,SiON, SiC, and SiCN layer. The removal of the sacrificial metal oxidepattern and the sacrificial via protecting layer is preferably performedby wet etching the sacrificial metal oxide pattern and the sacrificialvia protecting layer together using HF solution as an etchant.Specifically, if the sacrificial via protecting layer is formed of ahydrogen-siloxane layer such as HSQ, the sacrificial metal oxide patternand the sacrificial via protecting layer can be removed by wet etchingthem together using HF solution as an etchant. Therefore, a process ofremoving the sacrificial metal oxide pattern and the sacrificial viaprotecting layer can be simplified. However, if the sacrificial viaprotecting layer is formed of an organo-siloxane layer, such as MSQ, oran organic polymer, the sacrificial via protecting layer may not beremoved just using HF solution as an etchant. In this case, thesacrificial metal oxide pattern may be removed using HF solution as anetchant, and then, the sacrificial via protecting layer may be removedusing an organo stripper.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the more particular description of apreferred embodiment of the invention, as illustrated in theaccompanying drawings in which like reference characters refer to thesame parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1 is a sequential flow chart illustrating a method of forming adual damascene metal interconnection according to one embodiment of thepresent invention.

FIGS. 2 to 11 are sectional views illustrating a method of forming adual damascene metal interconnection according to one embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. In the drawings, the thickness of layers andregions are exaggerated for clarity.

FIG. 1 is a sequential flow chart illustrating a method of forming adual damascene metal interconnection according to an embodiment of thepresent invention, and FIGS. 2 to 11 are sectional views illustrating amethod of forming a dual damascene metal interconnection according tothe sequential flow chart of FIG. 1.

Referring to FIGS. 1 and 2, there is prepared a semiconductor substrate51 having a lower interconnection 53 (step 1 of FIG. 1). The lowerinterconnection 53 may be formed using a damascene process. Further, thelower interconnection 53 may be a copper interconnection, and adiffusion barrier layer (not shown) may be formed on the side walls andthe bottom of the copper interconnection 53.

Further, the semiconductor substrate 51 may have discrete devices suchas a transistor (not shown) or a capacitor (not shown).

An interlayer insulating layer 57 is formed on the semiconductorsubstrate 51 (step 3 of FIG. 1). Before forming the interlayerinsulating layer 57, an etch barrier layer 55 may be first formed. Inthe case that the lower interconnection 53 is a copper interconnection,the etch barrier layer 55 may function as a barrier to suppressout-diffusion of copper atoms into other layers. Furthermore, the etchbarrier layer 55 functions to protect the lower interconnection 53 frometch damages, which may occur in subsequent processes. Thus, the etchbarrier layer 55 is preferably formed to include a material layer suchas SiN, SiC, or SiCN. Typically, since the etch barrier layer 55 mayhave a high dielectric constant, preferably, the etch barrier layer 55is formed to have a thickness as thin as possible, but is sufficientlythick to serve as a barrier layer. The etch barrier layer 55 may beformed with a thickness of 500 Å to 1,000 Å, and more preferably, it isformed with a thickness of 600 Å to 800 Å.

The interlayer insulating layer 57 functions to isolate theinterconnections from one another. The interlayer insulating layer 57may be formed of a low-k dielectric layer to reduce a RC delay to complywith a recent demand for more and more highly-integrated semiconductordevices. Further, the interlayer insulating layer 57 may have an etchselectivity with respect to the etch barrier layer 55.

The interlayer insulating layer 57 may be formed of an SiOC layer or anSiO₂ layer, such as FSG, PSG, USG, BPSG, PE-TEOS layer, and it may beformed by stacking at least two of the above layers. Further, theinterlayer insulating layer 57 may be formed of organic polymer having alow dielectric constant, such as SiLK.

A first photoresist layer is formed on the interlayer insulating layer57. Then, the first photoresist layer is exposed and developed to form afirst photoresist pattern 61 having an opening 61 a over the lowerinterconnection 53. Before forming the first photoresist layer, a bottomanti-reflective coating (BARC) 59 may be formed. The BARC 59 ispreferably formed of an organic material. Thus, the BARC 59 is exposedthrough the opening 61 a over the lower interconnection 53.

Referring to FIGS. 1 and 3, the BARC 59 and the interlayer insulatinglayer 57 are sequentially etched using the first photoresist pattern 61as an etch mask to form a preliminary via hole 63 (step 5 of FIG. 1).Through the preliminary via hole 63, the etch barrier layer 55 may beexposed.

The interlayer insulating layer 57 may be formed of a material layerhaving an etch selectivity with respect to the etch barrier layer 55.Thus, the etch barrier layer 55 may remain on the lower interconnection53. As such, etch damage of the lower interconnection 53 is preventedduring the formation of the preliminary via hole 63.

In the case in which the interlayer insulating layer 57 is formed of anSiO₂ layer or an SiOC layer, after forming the preliminary via hole 63,the first photoresist pattern 61 and the BARC 59 are removed using, forexample, an ashing process. In the case in which the BARC 59 is formedof organic material, the first photoresist pattern 61 and the BARC 59may be removed at the same time using an ashing process.

Further, in the case in which the interlayer insulating layer 57 isformed of an organic polymer such as SiLK, the preliminary via hole 63may be formed using an ashing process. Thus, the first photoresistpattern 61 and the BARC 59 may be removed during the formation of thepreliminary via hole 63.

Referring to FIGS. 1 and 4, a sacrificial via protecting layer 65 isformed on the semiconductor substrate having the preliminary via hole 63(step 7 of FIG. 1). The sacrificial via protecting layer 65 fills thepreliminary via hole 63, and covers the upper surface of the interlayerinsulating layer 57.

The sacrificial via protecting layer 65 may be formed of a spin ondeposition (SOD) layer which is dry etched at a dry etch rate which issubstantially identical to that of the interlayer insulating layer 57,and has a significantly high wet etch selectivity with respect to theinterlayer insulating layer 57. The SOD layer is a layer which isdeposited using a spin coating. The SOD layer may be a hydrogen-siloxanelayer such as HSQ, an organo-siloxane layer such as MSQ, or a spin onpolymer (SOP) layer. Since the SOD layer exhibits good via hole fillingcharacteristics and good planarization characteristics, it can benormally used as filling material or planarization material.

Further, the SOD layer is preferably formed of a transparent layer in awavelength region for alignment, that is, a visible wavelength region,for a subsequent alignment process.

The sacrificial via protecting layer 65 may be formed with a thicknessof 500 Å to 3,000 Å.

A sacrificial metal oxide layer 67 is formed on the sacrificial viaprotecting layer 65 (step 9 of FIG. 1). As the sacrificial viaprotecting layer 65 covers the upper surface of the interlayerinsulating layer 57, the sacrificial metal oxide layer 67 may be formedflat.

The sacrificial metal oxide layer 67 may be formed of Al₂O₃, InSnO,Ta₂O₅, La₂O₃, or HfO₂ layer, or alternatively, it may be formed bystacking at least two layers of the above. Further, the sacrificialmetal oxide layer 67 may be formed with a thickness of 200 Å to 1,000 Å.As the thickness of the sacrificial metal oxide layer 67 decreases, theprocess margin of a photolithography process increases. But, thesacrificial metal oxide layer 67 should keep an appropriate thickness,since it is used as an etch mask in a subsequent process.

The sacrificial metal oxide layer 67 may be formed using a physicalvapor deposition (PVD) technology. That is, the sacrificial metal oxidelayer 67 may be formed by sputtering a metal target in the presence ofplasma containing oxygen atoms.

Alternatively, the sacrificial metal oxide layer 67 may be formed usinga typical atomic layer deposition (ALD) technology, or a chemical vapordeposition (CVD) technology.

Referring to FIGS. 1 and 5, a second photoresist layer is formed on thesacrificial metal oxide layer 67. The second photoresist layer isexposed and developed to form a second photoresist pattern 73 having anopening 73 a crossing over the preliminary via hole 63.

The second photoresist pattern 73 is preferably formed using an ArFlaser. By doing so, a process margin such as a resolution and DOF in thephotolithography process may be increased.

Further, the sacrificial metal oxide layer 67 is preferably formed of atransparent layer in a wavelength region for alignment, that is, avisible wavelength region, for a subsequent alignment process. If thesacrificial metal oxide layer 67 is transparent, there is no need of anadditional process to align the second photoresist pattern 73 on thepreliminary via hole 63.

Before forming the second photoresist layer, an organic BARC 71 may beformed. Specifically, the formation of the organic BARC 71 is used inthe photolithography process of forming the second photoresist pattern73 using an ArF laser. The organic BARC 71 functions to reducereflectivity of the sacrificial metal oxide layer 67, and control a CDand a CD uniformity of the second photoresist pattern 73.

Further, before forming the organic BARC 71, a capping layer 69 may befurther formed. The capping layer 69 functions as an inorganic BARC,thereby further reducing the reflectivity of the sacrificial metal oxidelayer 67.

The capping layer 69 may be formed of a poly-Si, FSG, PSG, USG, PE-TEOS,SiOC, SiN, SiON, SiC, or SiCN layer. Further, the capping layer 69 ispreferably formed with a thickness of 100 Å to 500 Å.

Since the capping layer 69 and the organic BARC 71 are additionallyformed, the reflectivity can be reduced, and the process margin of thephotolithography process of forming the second photoresist pattern 73can be further ensured. Therefore, even though the sacrificial viaprotecting layer 65 is transparent, the reflectivity may be reduced.

Referring to FIGS. 1 and 6, the organic BARC 71, the capping layer 69,and the sacrificial metal oxide layer 67 are sequentially etched usingthe second photoreist pattern 73 as an etch mask to form a capping layerpattern 69 a and a sacrificial metal oxide pattern 67 a (step 11 of FIG.1). The capping layer pattern 69 a and the sacrificial metal oxidepattern 67 a have an opening 67 b crossing over the preliminary via hole63 and exposing the sacrificial via protecting layer 65.

The second photoresist pattern 73 is used as an etch mask while etchingthe organic BARC 71, the capping layer 69, and the sacrificial metaloxide layer 67. Thus, even though the second photoresist pattern 73 isformed employing a photoresist layer for ArF laser, which has a low etchresistance, a desired etch process margin may be ensured.

Further, after forming the capping layer pattern 69 a and thesacrificial metal oxide pattern 67 a, the second photoresist pattern 73and the organic BARC 71 are removed using a typical method such as anashing. Alternatively, the second photoresist pattern 73 and the organicBARC 71 may be removed after forming a trench.

Referring to FIGS. 1 and 7, the exposed sacrificial via protecting layer65 and the interlayer insulating layer 57 are etched using the cappinglayer pattern 69 a and the sacrificial metal oxide pattern 67 a as etchmasks to form a trench 75 (step 13 of FIG. 1). The trench 75 may beformed inside the interlayer insulating layer 57 with a depth of 1,500 Åto 6,000 Å. The trench 75 may be formed by dry etching the sacrificialvia protecting layer 65 and the interlayer insulating layer 57. The dryetch is preferably performed under the conditions that the etch rates ofthe sacrificial via protecting layer 65 and the interlayer insulatinglayer 57 are substantially identical, or a ratio of the etch ratesbetween the sacrificial via protecting layer 65 and the interlayerinsulating layer 57 is lower than 4:1.

Typically, the sacrificial metal oxide pattern 67 a has a relativelyhigh etch selectivity with respect to the interlayer insulating layer57. Thus, during the formation of the trench 75, the sacrificial metaloxide pattern 67 a is not completely removed and can carry out itsfunction as an etch mask. However, as the capping layer pattern 69 a isetched at an etch rate similar to that of the interlayer insulatinglayer 57, it may be all removed during the formation of the trench 75.

Further, the sacrificial via protecting layer 65 is dry etched at anetch rate substantially identical to that of the interlayer insulatinglayer 57, or is dry etched at an etch rate, which is slightly high incomparison with that of the interlayer insulating layer 57. Thus, thesacrificial via protecting layer 65 inside the preliminary via hole 63is etched along with the interlayer insulating layer 57. Thus, duringthe formation of the trench 75, a part of the sacrificial via protectinglayer 65 remains inside the preliminary via hole 63. As a result, theetch barrier layer 55 under the preliminary via hole 63 may be protectedfrom the etch. Accordingly, etch damage of the lower interconnection 51may be prevented.

Referring to FIGS. 1 and 8, after forming the trench 75, the sacrificialmetal oxide pattern 67 a and the sacrificial via protecting layer 65 areremoved. If the sacrificial via protecting layer 65 is formed ofhydrogen-siloxane such as HSQ, the sacrificial metal oxide pattern 67 aand the sacrificial via protecting layer 65 are preferably wet etchedusing HF solution as an etchant, and removed at the same time.

In the case in which the sacrificial via protecting layer 65 is formedof an organo-siloxane layer such as MSQ, or an SOP, the sacrificial viaprotecting layer 65 may not be removed using a HF solution as anetchant. In this case, the sacrificial metal oxide pattern 67 a is wetetched using a HF solution as an etchant, and the sacrificial viaprotecting layer 65 may be removed using an organo stripper. In thiscase, an etchant used in the organo stripper may be varied depending onthe kinds of the sacrificial via protecting layer 65.

As a result of removing the sacrificial via protecting layer 65 and thesacrificial metal oxide pattern 67 a, the upper surface of theinterlayer insulating layer 57 is exposed, and the etch barrier layer 55is exposed through the preliminary via hole.

Referring to FIGS. 1 and 9, the exposed etch barrier layer 55 is removedto form a final via hole 63 a exposing the lower interconnection 53(step 15 of FIG. 1). The etch barrier layer 55 may be etched using anetchant having a high etch selectivity with respect to the interlayerinsulating layer 57.

Further, the lower interconnection 53 and the etch barrier layer 55 areprevented from being etched by the sacrificial via protecting layer 65during the formation of the trench 75. Thus, the etch barrier layer 55may have a thickness relatively small in comparison with that of theinterlayer insulating layer 57. Thus, the etch barrier layer 55 can beetched without damage to the profiles of the trench 75 and thepreliminary via hole 63.

Referring to FIGS. 1 and 10, a conductive layer 81 is formed on thesemiconductor substrate having the final via hole 63 a and the trench 75by a typical method (step 17 of FIG. 1). The conductive layer 81 may bea copper layer. Further, before forming the copper layer, a conformaldiffusion barrier metal 77 and a seed layer 79 may be formed. The copperlayer may be formed using an electrolytic plating technology or anelectroless plating technology, and it may fill the empty space of thetrench 75 and the final via hole 63 a.

Referring to FIGS. 1 and 11, until the upper surface of the interlayerinsulating layer 57 is exposed, the conductive layer 81, the seed layer79, and the diffusion barrier metal 77 are planarized using a CMPtechnology (step 19 of FIG. 1). As a result, there are formed adiffusion barrier layer 77 a, a seed layer 79 a, and a metalinterconnection 81 a, which are confined inside the trench 75, and thereis formed a via plug for filling the final via hole 63 a. The metalinterconnection 81 a is electrically connected to the lowerinterconnection 53 through the via plug formed inside the final via hole63 a.

Accordingly, the embodiments of the present invention are effective inthat process margins are ensured, i.e., the use of the sacrificial metaloxide layer 67 provides a process margin in a photolithography processof forming a trench, and the use of the sacrificial metal oxide pattern67 a as an etch mask for the formation of the trench 75 allows a processmargin in an etch process. Further, by additionally forming the cappinglayer 69 on the sacrificial metal oxide layer 67, a reflectivity withrespect to lower layers may be further reduced. As a result, a CD and aCD uniformity may be adjustable, thereby further improving a processmargin of a photolithography process.

Further, since the sacrificial metal oxide layer 67 has a great lighttransmittance unlike metals, there is no need for an additional processof aligning the second photoresist pattern 73 on the preliminary viahole.

While this invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

1. A method of forming a dual damascene metal interconnectioncomprising: a) preparing a semiconductor substrate; b) forming aninterlayer insulating layer on the semiconductor substrate; c)patterning the interlayer insulating layer to form a preliminary viahole; d) forming a sacrificial via protecting layer, a first portion ofthe sacrificial via protecting layer filling the preliminary via holeand a second portion of the sacrificial via protecting layer covering anupper surface of the interlayer insulating layer at the outside of thepreliminary via hole on the semiconductor substrate having thepreliminary via hole; e) forming a sacrificial metal oxide layer on boththe first and second portions of the sacrificial via protecting layer;f) patterning the sacrificial metal oxide layer to form a sacrificialmetal oxide pattern having an opening exposing the first portion and aportion of the second portion of the sacrificial via protecting layer;and g) etching the sacrificial via protecting layer and the interlayerinsulating layer using the sacrificial metal oxide pattern as an etchmask to form a trench located inside the interlayer insulating layer. 2.The method according to claim 1, wherein the sacrificial metal oxidelayer is transparent in a visible wavelength region.
 3. The methodaccording to claim 2, wherein the sacrificial metal oxide layer isformed of at least one metal oxide layer selected from the groupconsisting of Al₂O₃, InSnO, Ta₂O₅, La₂O₃, and HfO₂.
 4. The methodaccording to claim 3, wherein the sacrificial metal oxide layer isformed with a thickness of about 200 Å to 1,000 Å.
 5. The methodaccording to claim 4, further comprising forming an etch barrier layerprior to formation of the interlayer insulating layer.
 6. The methodaccording to claim 5, further comprising forming an organic BARC on thesacrificial metal oxide layer after forming the sacrificial metal oxidelayer.
 7. The method according to claim 6, further comprising removingthe organic BARC prior to formation the trench.
 8. The method accordingto claim 7, wherein the organic BARC is removed using an ashing process.9. The method according to claim 6, further comprising forming a cappinglayer on the sacrificial metal oxide layer prior to formation of theorganic BARC.
 10. The method according to claim 9, wherein the cappinglayer is formed of a material layer selected from the group consistingof poly-Si, FSG, PSG, USG, PE-TEOS, SiOC, SiN, SiON, SiC, and SiCNlayer.
 11. A method of forming a dual damascene metal interconnectioncomprising: a) preparing a semiconductor substrate; b) forming aninterlayer insulating layer on the semiconductor substrate; c)patterning the interlayer insulating layer to form a preliminary viahole; d) forming a sacrificial via protecting layer, a first portion ofthe sacrificial via protecting layer filling the preliminary via holeand a second portion of the sacrificial via protecting layer covering anupper surface of the interlayer insulating layer at the outside of thepreliminary via hole on the semiconductor substrate having thepreliminary via hole; e) forming a sacrificial metal oxide layer on boththe first and second portions of the sacrificial via protecting layer;f) forming a photoresist layer on the sacrificial metal oxide layer; g)exposing and developing the photoresist layer using an ArF laser to forma photoresist pattern having an opening crossing over the preliminaryvia hole; h) etching the sacrificial metal oxide layer using thephotoresist pattern as an etch mask to form a sacrificial metal oxidepattern having an opening exposing the first portion and a portion ofthe second portion of the sacrificial via protecting layer; and i)etching the sacrificial via protecting layer and the interlayerinsulating layer using the sacrificial metal oxide pattern as an etchmask to form a trench located inside the interlayer insulating layer.12. The method according to claim 11, wherein the sacrificial metaloxide layer is transparent in a visible wavelength region.
 13. Themethod according to claim 12, wherein the sacrificial metal oxide layeris formed of at least one metal oxide layer selected from the groupconsisting of Al₂O₃, InSnO, Ta₂O₅, La₂O₃, and HfO₂.
 14. The methodaccording to claim 13, wherein the sacrificial metal oxide layer isformed with a thickness of about 200 Å to 1,000 Å.
 15. The methodaccording to claim 14, further comprising: forming an etch barrier layerprior to formation of the interlayer insulating layer.
 16. The methodaccording to claim 15, further comprising: forming an organic BARC onthe sacrificial metal oxide layer after forming the sacrificial metaloxide layer.
 17. The method according to claim 16, further comprising:removing the organic BARC prior to formation of the trench.
 18. Themethod according to claim 17, wherein the organic BARC is removed usingan ashing process.
 19. The method according to claim 16, furthercomprising: forming a capping layer on the sacrificial metal oxide layerprior to formation of the organic BARC.
 20. The method according toclaim 19, wherein the capping layer is formed of one material layerselected from the group consisting of poly-Si, FSG, PSG, USG, PE-TEOS,SiOC, SiN, SION, SiC, and SiCN layer.